Rockwell Automation 7000L PowerFlex 7000 Medium Voltage AC Drive C Frame - Marine - Manual (Page 186)

4-10 Component Definition and Maintenance
7000L-UM302B-EN-P – June 2013 7000 ―C‖ Frame - Marine
Surge Arresters (cont.)
There are three Y-connected surge arresters attached to the incoming MV
lines. The neutral point of the arresters is connected to the ground bus.
U
Heavy duty
distribution
class surge
arrester
W V
Drive input power from
line terminals
Operation
The operation of arresters without a gap is the same as that of MOVs in
the TSN. Depending on design, the arrester may also be gapped. Both
gapped and un-gapped arresters provide adequate overvoltage protection.
The arresters are able to withstand or ride through most commonly seen
bus transients within their capability. However, caution should be taken
if there is a harmonic filter on the MV bus to which PF7000 is
connected. The filter should satisfy relevant international or local
standards, such as IEEE Std 1531— Clause 6.4, to avoid high inrush
currents.
The surge arrester is certified as per ANSI/IEEE Std C62.11-1993.
Certification tests include high current short duration tests, low current
long duration tests and fault current withstand tests. The fault current
withstand tests consist of different combinations of kA and number of
cycles, including a 20kA 10-cycle test, under which the arresters are non-
fragmenting and without expelling any internal components.
When the incoming energy exceeds the handling capability of the
arrester and causes arrester failure, the housing is designed to split open
to vent without causing damage to any adjacent components.